Electric soldering iron



May 16, 1933. E. H. LINDHOLM ELECTRIC SOLDERING IRON Filed Feb.

avwem foz ERNEST H L/NDHOLM Patented May 16, 1933 UNITED STATES PATENT OFFICE ELECTRIC SOLDERING IRON Application filed. February 19, 1930. Serial No. 429,472.

This invention relates to the construction of an electric soldering iron and has for its principal object the provision of improvements in the details covering the mechanical and electrical features, whereby a more rugged and substantial implement is secured.

Another object of my invention is to provide such improvements in the mechanical details as will improve the electrical or heat-- ing efliciency of the implement.

Another object of my invention is to pro- Vide a construction whereby the life of the implement may be materially increased.

These and other objects will be readily understood by one familiar with the construction of a soldering iron, after a reading of the specification taken in connection with the annexed drawing, wherein:

Figure 1 is a part-sectional, part-elevational view through the implement without the tip; and the tip-end being unfinished.

Figure 2 is a view of the right-hand end of the implement shown in Figure 1, without the handle, the view being taken at right angles to that shown in Figure 1.

Figure 3 is a view of substantially double size of the left-hand end of Figure 1, onehalf being shown in finished condition to receive the tip.

Figure 4 is a sectional View through the left-hand end of Figure 1 after this end has been finished to receive the tip.

Figure 5 is a plan View of the terminal strip, double size.

Figure 6 is a view of the terminal strip screw bushing.

Figure 7 is an end View of Figure 6.

Figure 8 is a side view of the core insulator.

Figure 9 is an end view of Figure 8.

Figure 10 is a plan view of the sealing bushing with sealing tubes attached thereto.

Figure 11 is an end View of Figure 10.

I Figure 12 is a plan View of the tip-end of the implement showing the soldering tip in position.

Referring now to the details wherein like numbers refer to corresponding parts in the various views, 1 is a metal shell preferably of steel, which as illustrated, is drawn down or formed into sections of three different diameters.

The left-hand section contains the core 2 which is of a metal of high conductivity, such as copper. One end of the core 2 has a cavity 3, the purpose of which will be hereinafter explained. Around the core 2 is an insulator 4, such as mica, capable of withstanding a high heat; and disposed on this insulator, is a heating coil 5 of suitable highresistance wire, such as nichrome. Exterior to the heating coil 5, is a further insulator 6 which is similar to the insulator 4.

Positioned against the end of the core 2 is an insulator 7 preferably of high-heatresistance material such as lava. The insulator 7 has a groove 8 in one end which is adapted to receive the metal 9 of the core 2 which is spun over into the groove 8, thereby securely locking the insulator 7 in position. It will be noted in Figure 1, that the insulators 4 and 6 preferably overlap and rest on the annular shoulder 10 of the in sulator 7 The insulator 7 is provided with a plurality of diagonally arranged holes 11, through which the lead wires extending from the coil 5 may be positioned. In the view shown in Figure 1, the section through the insulator 7 is such that the holes 11 do not show.

Positioned within the central and righthand portions of the protecting shell 1, is a tube 12 preferably of high heat-resistance material such as lava. The tube 12 is pro vided with a pair of holes 13, through which the lead wires extend. Positioned against the outer end of the tube 12, is a sealing bushing 14 which preferably is pressed into the reduced end of the shell 1. The bushing 14 is preferably made of strong heat resisting material and has mounted thereon in any satisfactory manner, a pair of sealing tubes 15 and 16, having passages 17 and 18 provided for the lead wires coming from the heating coil 5.

Mounted on the outer end of the shell 1 is a terminal strip 19. One end of the strip 19 has a pair of notches 20 therein and a shoulder 21 which is adapted to fit against the end 22 of the shell 1. After the terminal strip 19 has been forced into position, as ust indicated, the metal of the shell at 23 1s punched downwardly into the notches 20, thereby locking th terminal strip 19 securely in position in the end of the shell 1.

The terminal strip 19 is provided with a pair of round holes 24, into each of which, are driven from opposite sides of the strip 19, terminal bushings 25 which have sides that are substantially at right angles to each other and which therefore cut their way into the material of the insulator strip 19, which may be of fibre, thereby being locked in position in the strip 19. These bushings 25 are for the purpose of receiving terminal screws 26 for fastening the terminals 27 to which the lead wires are attached, which lead wires 1 come through the passages 17 and 18 of the tubes 15 and 16 as previously explained. The same screws 26 also serve to clamp the terminals 28, to which are attached the two wires comprising the cable 29 by which the electrical current is brought to the soldering llOl'l.

It will be noted that the cable end of the terminal strip 19 terminates in two forked members 30 and 31, between which is a throat 32 somewhat narrower than the width of the cable 29. Preferably the insulation adjacent the terminals 28 is covered with tape or binding twine, or both, so as to prevent the insulation on the cable from fraying out. At the same time, this enlarged portion of the cable 29 is adapted to lie in the recess 33, while the throat 32 grips the cable back of this re-enforcement 45.

A groove 34 is preferably provided for the pur ose of receiving a snap ring 35 or a stout in ing wire, thereby holding the forked ends 30 and 31 from spreading. From this construction, it will be readily appreciated that the cable 29 is very securely anchored to the terminal strip 19. It is to be noted that when the terminals 27 are soldered to the leads coming through the tubes 15 and 16, the soldering operation should be such as to absolutely seal the outer ends of the passages 17 and 18, and since the tubes 15 and 16 are tightly anchored to the sealing bushing 14 and this in turn is press-fitted into the shell 1, the outer end of the shell 1 is hermetically sealed for the purpose to be hereinafter pointed out.

At the junction of the middle and righthand end section of the shell 1, the metal is preferably bulged outwardly at 36 to provide a positioning means for a handle 37 which may be made of any suitable material and which is shown in dotted position. The handle 37 is preferably provided with an interior bushing or ferrule 38 which is adapted to be screwed on to the screw threads 39 which may be rolled into the material of the shell 1, all as shown in Figure 1.

Another important part of the construction of the soldering iron is found in the means for carrying the tip. It will be noted in Figure 1 that the core 2 is supported at the outer end by a metallic collar 40 which is preferably first pressed on the core 2 and then placed in the shell 1. The outer end of the shell 1 is provided with a plurality of anchor members 41. These anchor members are bent inwardly as shown in Figure 4, and molten metal, preferably of brass with a high percentage of copper, is poured into the cavity 3 and all around the anchor members 41 and the collar 40. This molten metal makes a complete weld or union with the core 2 and th anchor members 41, thereby anchoring the core securely and preventing its turning when the soldering tip is put in or removed for changing the tip. This mold- 111g operation also hermetically seals the tipend of the shell 1.

After this molding operation has been performed, a hole 42 is drilled and tapped as shown in Figure 4, to receive a threaded end of a soldering tip 43. In the molding operation a central tube may be positioned in the cavity 3 so as to assist in the drilling operation after the casting operation has been performed. The use of such a tube also assists in allowing the air in the cavity 3 to escape, so that no air is trapped in the cavity 3 during the casting operation.

As shown in Figure 4, the outer end of the metal which is used in making the casting, is counter-sunk at 44, so as to provide a large area of contact with the tip 43, which tip or tips are provided with a seat to fit this counter-sunk surface 44.

In addition to anchoring the core in fixed position in the shell 1, it is to be observed that this method of anchoring the core 2 and mounting the tip, provides means for obtainmg an excellent mechanical connection with the soldering tip 43.

It is to be noted that the shell 1 is hermetically sealed at both ends, thereby preventing oxidation on the interior of the shell and of the core. If air were allowed to have free access to these parts, the oxidation would be so great as to cause scale to form within the interior of the shell 1, and this scale would work in at the ends of the winding of the heating coil 5 and would either short-circuit or ground the heating coil 5. These troubles are eliminated by my construction. F urthermore, by sealing the terminal end of the implement, the heat is prevented from coming out of the handle end, thereby making the implement easier to handle. In addition to preventing scale from forming, as has been described, the life of the resistance wire is also increased by keeping the air away from it.

While I have shown a practical form of carrying my improvements into operation, it is to be understood that I do not wish to be limited to the precise details shown, as these may be varied without departing from the spirit of my invention or the scope of the appended claims; for example, the spacing collar 40 may be made integral with the core 2 by upsetting the end thereof.

Having thus described my invention, what I claim is:

1. An electric soldering iron including; a one piece metal shell, a metallic core member positioned in one end of the shell, a winding on said core but insulated therefrom and from the shell, an insulator closely adjacent the inner end of the core, a collar for spacing the core from the shell at the tip-end, said shell having anchor members at the tip end extending toward the axis of the core, metallic means surrounding said anchor members and forming a union with said core, means for fastening a soldering tip to said metallic means, a terminal strip positioned in and rigidly fastened to the handle end of the shell, a sealing bushing positioned in the shell adjacent the inner end of said strip, metallic sealing tubes carried by said bushing through which lead wires from said winding may pass, means carried by said terminal strip for attaching incoming conductors and the coil lead wires together, and a handle carried by the shell over said terminal strip.

2. An electric soldering iron including; a one-piece metallic shell, a heating unit consisting of; a metallic core, a lead wire insulator attached to the core and a winding of resistance wire wound on, but insulated from, the core; said heating unit being hermetically and immovably sealed in the shell by the following instrumentalities; a bushing on the core, spacing it from the shell, anchor members extending from the shell toward the axis of the core, metallic means surrounding said anchor members and forming a complete union between the shell, bushing and core, a sealing bushing tightly fitting the other end of the shell, said bushing carrying tube terminals for lead wires coming from said heating winding, the outer ends of said tubes being completely soldered over and to the leadin wires which pass therethrough; means for mounting a soldering tip in the end of said core, a terminal strip fastened to the handle end of the shell, and means on said strip for attaching said lead wires and an incoming cable thereto.

3. In an electric soldering iron, a heating unit consisting of; a metallic core, a lead wire bushing adjacent one end of the core and a winding of resistance wire on, but insulated from, the core; means for keeping air away from the winding including; a shell adapted to receive the heating unit in one end, and a sealing bushing at the other end, said shell having anchor members adjacent the outer end of said core and metallic means surrounding said anchor members and forming a complete union and seal between the shell and the core, a sealing bushing tightly fitting in the other end of the shell, said bushing having sealing tubes through which lead wires from the winding may pass, said lead wires and respective tube-ends being soldered together so as to close the tube opening; means for mounting a soldering tip in the end of said core, a. terminal strip fastened to the handle end of the shell, and means on said strip for attaching said lead wires and incoming cable thereto.

4. In an electric soldering iron, a heating unit consisting of; a metallic core, a lead wire bushing adjacent one end of the core and a winding of resistance wire on, but insulated from, the core; a one-piece metallic shell carrying the core and winding in one end thereof, means for sealing the ends of the shell including; anchor members in the shell adjacent the tip-end of the core, metallic means surrounding said anchor members and forming a union and seal between the shell and the core, a sealing bushing tightly fitting in the other end of the shell, said bushing having sealing tubes through which lead wires from the winding may pass, said lead wires and respective tube-ends being soldered together so as to close the tube opening, means for mounting a soldering tip in the end of said core, a terminal strip fastened to the handle end of the shell, and means on said strip for attaching said lead wires and an incoming cable thereto.

5. In a soldering iron including a metallic shell and heating unit, said heating unit including a metal core having a cavity at one end and a winding of resistance wire on the core; means for mounting the heating unit in the shell comprising a plurality of anchor members extending from the end of the shell toward the axis of said core, said anchor members being embedded in met-a1 poured whil in a molten state into the cavity and around the end of the core and within the end of the shell, metallic means at the other end of the shell for sealing this end of the shell, and further means carried by the latter end of the shell adjacent said sealing means for completing connections to said winding, and means for attaching a soldering tip to said core.

6. In an electric soldering iron having a shell and a heating unit comprising a metallic core and winding thereon in one end of the shell, means for anchoring said unit in the shell including; anchor members extending from the end of the shell toward the axis of said core, said core initially having a cavity, said anchor members being embedded in metal poured while in a molten state into said cavity and around the end of the core and within the end of the shell; said cavity being rebored and adapted to receive a soldering tip therein.

7. An electric soldering iron as set forth in claim 2, further characterized in that the terminal strip has a shoulder and notch at one end to be engaged by part of the shell to securely hold the strip in place, terminal screw bushings carried by said strip, one

end of the strip being forked to form a throat leading into a recess, said recess receiving the reinforced end of a current supply cable, said throat gripping said cable, said forked ends having a groove therein and a binding member in said groove to cause said throat to maintain its grip on the cable.

8. An electric soldering iron as set forth in claim 5, further characterized in that said further means for completing the connection to said winding includes a terminal strip in the handle end of the shell, with means cooperating between the end of the shell and said strip to hold the strip securely to the shell, terminal screw bushings attached to the strip in spaced relation, the free end of the strip being forked to receive the end of a current supply cable, said forked ends being adapted to receive a securing means to hold said forked ends in gripping position on the cable.

9. An electric soldering iron as set forth in claim 5, characterized in that said further means for completing the connection to said winding includes a terminal strip in the handle end of the shell, said terminal strip being flat and relatively thin and attached to the shell on a diameter of the same, said attachment being attained by means of a shoulder and a notch near one end of the strip, the shoulder engaging the end of the shell and a part of the shell being depressed into said notch, said strip having terminal screw bushings mounted on opposite sides of and near the center of the strip, said strip having its free end forked to receive a supply cable, and means cooperating with the forked ends of the strip to cause said ends to permanently grip the cable.

10. An electric soldering iron having a one-piece shell, a heating unit located in one end of the shell and a terminal strip in the other end, means for sealing the heating unit within the shell; said means comprising, a metal core for the heating unit having an initial cavity therein, anchor members at the ERNEST H. LINDHOLM. 

